KR20110128851A - Method for communicating in a network comprising a batteryless zigbee device, network and device therefor - Google Patents

Abstract

The present invention relates to a method for wirelessly communicating in a network comprising a resource constrained end device and a first router device, the method comprising: sending, by an end device (ZBLD), a trigger for a proxy discovery procedure; The router R1 device receiving a trigger for a proxy discovery procedure, determining whether the first router R1 meets conditions for operating as a router for an end device, and if the conditions are met And designating itself as a proxy router for the end device, so that the first router relays communication between the end device and the rest of the network. The invention also relates to end devices, router devices, and networks therefor.

Description

TECHNICAL FOR COMMUNICATING IN A NETWORK COMPRISING A BATTERYLESS ZIGBEE DEVICE, NETWORK AND DEVICE THEREFOR}

The present invention relates to a method for communicating in a radio control network. In particular, the present invention relates to a method for ensuring maintenance of a communication link between a communication device and a router in a wireless network.

This invention relates to wireless networks, including, for example, devices with low power resources. In a particular application, the present invention relates to wireless networks using communication protocols that conform to IEEE802.15.4 and IEEE802.15.4-based protocols, eg, the Zigbee protocol.

Radio control networks have recently become a very common trend in the field of communications, especially for building management systems. Wireless technologies offer major advantages in terms of freedom of deployment, portability, and reduced installation costs, as there is no need to pull out and puncture cables. Accordingly, these techniques require the installation of one device from another device and for example in locations remote from devices that control lighting, such as light switches, light dimmers, wireless remote controllers, movement or light detectors. It is particularly effective at interconnecting, detecting, automating, controlling and monitoring systems using sensor devices such as those.

One of the drawbacks seen in networks and the like relates to powering devices. In fact, because the devices are not wired, they can no longer receive the power needed to perform all the operations necessary in the network from the mains or via a connection with a controller. Accordingly, it has been envisioned to have such devices equipped with built-in batteries. However, because the devices are quite size constrained, the batteries may not be large, resulting in reduced device life, or labor intensive battery replacement.

It has been proposed to solve this problem by equipping sensor devices with self-supporting energy sources that supply energy from their environment. However, the amount of energy that can be achieved by off-the-shelf energy self-containers is very limited, which means that the features and functions of battery-free devices are quite limited.

Among the functions that must be maintained for good operation in a wireless network is a link connection that makes it possible at any time to ensure that resource constrained devices are linked to routers that carry messages on their behalf. Therefore, in current implementations, a parent-child relationship is generally established between the resource constrained end device and its parent. The child end devices address all their communications to the parent to send to their final destination. However, in the case of energy- self-contained devices, this relationship leads to a single point of failure in the network since communication from the end device can no longer be successfully executed when the parent link is broken. Also, in most cases, such a failure may not even be detected by the end device, due to a path that is absent or not used, or insufficient energy.

Accordingly, there is a need for a communication chamber that ensures maintenance of good operation in a radio control network. In addition, as described above, there is a need for a method in which end devices are generally constrained in terms of resources, i.e., energy resources, without using too many resources of these devices.

It is an object of the present invention to propose a method for solving at least some of the above mentioned problems. In particular, it is an object of the present invention to provide a method of communication in a network comprising at least a resource constrained device, also called an end device, and at least one router device having a high resource, also called a router.

It is a further object of the present invention to propose a method which makes it possible to limit the power consumption at the end-device for the construction and / or maintenance of the network.

Another object of the present invention is to propose a method which eliminates the need to preconfigure the end device in advance.

It is yet another object of the present invention to provide a method that, in the event of a change in the network, avoids any performance limitations due to special relationships between preconfigured parent and resource constrained or batteryless devices.

To this end, the present invention relates to a method for wirelessly communicating in a network comprising a resource constrained end device and a first router device. Way

The end device sending a trigger for a proxy discovery procedure,

The first router device receiving a trigger for a proxy discovery procedure;

Determining whether the first router meets the conditions for operating as a router for an end device, and

If the conditions are met, the first router designating itself as a proxy router for the end device, in order to relay communication between the end device and the rest of the network.

In this way, the only action performed by the end device to resolve the proxy loss problem is to send a command frame to initiate the proxy discovery procedure. Accordingly, this method makes it possible to maintain sufficient operation in the network using as little energy as possible by the end device.

In an embodiment of the method according to the invention, the trigger for the proxy discovery procedure takes into account the identification of the end device. In this case, the decision step is:

Determining whether the first router device is linked to an end device based on the identification element,

Determining that the conditions are met if the end device is linked, and

If the end device is not linked, checking whether the first router device can link itself to the end device.

This method allows only the router device to determine whether it is linked to the end device. Within the meaning of the present invention, a router is linked to this end device when registered as a parent to the end device. In fact, the end device is absolutely unaware of the congestion of the router, which eliminates the need for any pre-configuration of the end device and allows it to automatically adapt to changing conditions and to parent replacement without further end device involvement. .

In another embodiment, the method according to the invention is:

Determining a performance indicator of a link between the end device and the first router device,

Comparing this performance indicator to a predetermined criterion, and

If the performance indicator meets a predetermined criterion, determining that the first router device can be a proxy router for the end device.

The performance indicator is for example a link cost indicator or the fact that the router application is controlled by the end device. This feature makes it possible to ensure that the router specified during the proxy discovery method according to the invention is a router that guarantees the best transmission performance in the network.

In a particular embodiment, the method according to the present invention includes a proxy resolution procedure that enables the router to inform other routers in the network of its intention to be a parent router to the end device that has initiated the proxy discovery procedure. For example, the proxy resolution procedure includes the router determining to be a parent to the device and sending a proxy resolution message. This message is sent after a delay determined, for example, based on the performance indicator of the link between the end device and the router.

The invention also relates to a method comprising a solution procedure in case two routers decide to be the parent router for one end device at the same time.

In addition, the present invention:

Wireless receiving means for receiving data frames and command frames from other devices in a wireless network,

Wireless transmission means for transmitting acknowledgment messages and resolution messages,

Means for transmitting end device messages,

Comparison means for comparing the address of the router device with other addresses, and

Memory means for storing a neighbor table, said table comprising a list of end devices and a state of a relationship between said router device and each end device.

Another aspect of the invention is:

Wireless transmission means for transmitting data and triggering a proxy search procedure;

Wireless transmission means for receiving at least acknowledgment messages;

Means for tracking acknowledgments and determining the proxy search procedure triggering; And

A terminal device, comprising limited energy resources.

Another aspect of the invention relates to a network comprising at least one end device and one router device according to the invention.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described below.

The invention will be described in detail with reference to the accompanying drawings as an example.

1 shows a network according to the invention;
2 is a block diagram of an operation sequence in a router device installed in a network according to the present invention.

The present invention relates to a method for communicating in a radio control network as shown in FIG. The network includes end devices. This device is, for example, a ZigBee battery-less device (ZBLD), but the present invention relates to a wireless device with any resource constraints, such as light switches, light dimmers, wireless remote controllers, mobile detectors, or light detectors. The same applies in particular to battery power use or energy-sustaining devices. The network also includes several router devices R1, R2, R3, R4, R5. These router devices comply with Zigbee communication protocols in a preferred embodiment. In another advantageous embodiment, ZigBee batteryless devices and routers conform to the lightweight 802.15.4-based batteryless protocol.

In this network, a relationship is established between R1, one of the routers in this example, and the end device. Each time the end device sends a frame, the router sends it. When the router correctly receives the transmitted frame, the router sends an acknowledgment message to the end device through the MAC layer. As long as the end device receives this MAC ACK frame for its transmission, it is confirmed that its network connection is valid. The end device does not know the identity of the router.

However, when the connection is lost, such a loss is identified by the missing ACK, and it is necessary to disclose a method for establishing a new connection in order to maintain correct communication in the network. As previously mentioned herein, the end devices used in these networks are resource constrained, especially in terms of power, so that the network can operate correctly without involving too much power for the end devices. It is necessary to provide ways to make it work. Accordingly, the present invention provides a method of fulfilling these requirements. When the end device has not received the acknowledgment message, the end device triggers a "proxy search" procedure to inform the surrounding router devices in the network that it has lost the parent and needs a new parent. Triggering the proxy search procedure may be done, for example, by sending a proxy search command frame or by re-sending it by inserting a flag in the data frame. Triggering is the only action performed by ZBLD in this proxy discovery procedure, which means that only a small amount of energy is required in the ZBLD to execute the method.

The advantage is that information about battery-free devices is stored in all routers in the neighbor of the end device and that the end device can be recognized as such. In this regard, in 802.15.4, each router comprises memory means for storing a neighbor table. In an embodiment, the information about ZBLD is stored in the "device type" field of the neighbor table entry. The table entry also includes a relationship field containing the type of relationship between the ZBLD and the router device, such as "child", "old child", "not applicable". In an alternative embodiment, the identifying element of the ZBLD is stored directly in the relationship field, with a relationship state such as "ZBLD child" or "ZBLD affinity".

The network according to the invention is a network which does not require ZBLD to require any special participation procedure. It is not configured with any parent address and the parent is not configured with the address of the ZBLD, which simplifies and shortens the installation and configuration procedure since it avoids any pre-configuration procedure. Accordingly, in the 802.15.4 / Zigbee network, the ZBLD only needs to be configured with a channel number, a network identifier (PANId), and a unique identifier (NWK address). In terms of application layer configuration, the ZBLD is preferably composed of the multicast addresses of a group of devices controlled by this ZBLD, which allows for flexible reconfiguration of group membership without involving the ZBLD. Accordingly, ZBLD uses group identifiers to address its application-layer command to the appropriate actuators that should be configured as group members. In Zigbee, these group identifiers are at the application support sub-layer or network level. Therefore, the ZBLD must be further configured with the group ID as the source, and all actuator devices to be controlled by this ZBLD must be configured as members of this group.

In the network according to the invention, the link between the ZBLD and the router is not fixed, which enables high mobility for both the ZBLD and the router, and also links between the end device and the router device without burden on the ZBLD side, for example. Due to the change in propagation conditions leading to disconnection, it enables automatic adaptation to parental replacement.

Thus, in the network according to the present invention, the normal operation of ZBLD appears to consist simply of sending data frames to other devices in the network. As described above, on the MAC level, the ZBLD sends a data frame to be sent by the proxy router and then waits for an acknowledgment message. Depending on the structure of this message and the nature of the ZBLD device communication, only the receipt of the acknowledgment message is not tracked or tracked, but the origin of the message is not tracked. Thus, when a message is actually received, the ZBLD does not need to know which router has processed its own outgoing message, and when the message is not received, the ZBLD cannot identify which link is broken and needs to verify. There is no.

Once the proxy discovery procedure is initiated, a proxy discovery command frame is received by one or several router devices in the network.

With reference to FIG. 2, the operations performed at a router device in a network when receiving a frame (“Rx frame”) will be described with reference to FIG. 2.

First, the router device checks whether the frame is from a ZigBee battery-free device ("from ZBLD"). This verification is performed, for example, by checking the contents of the device type field contained in the frame.

If the originator of the frame is actually a ZBLD, the router device determines whether the received frame initiates a proxy discovery procedure (“start proxy search”).

In the first case, assume that no proxy search has been initiated, i.e., the frame is completely a data frame. The router device determines whether the ZBLD that originated the frame belongs to its network ("ZBLD in NT"). The determination is performed, for example, by checking whether the identifier of the ZBLD is stored in the neighbor table of the router device. If the ZBLD is not already in the table, the router device adds it with a relation state of "no relation" ("ADD"). Conversely, if the ZBLD already exists in the table, the router device checks the relationship status of the ZBLD ("ZBLD = Child?"):

If the ZBLD is a child, the router device forwards the data frame and sends an acknowledgment message ("MAC ACK") to the ZBLD,

If the ZBLD is not a child, the router device buffers the data frame ("BUFFER") and activates the "proxy timeout". If a "proxy search" message is received for this particular ZBLD during the timeout and the router becomes a new parent, the router device forwards the data frame. Otherwise, the data frame is discarded.

Now assume that a frame triggers a proxy discovery procedure, for example, via a dedicated proxy discovery command frame sent by ZBLD, or via a flag set in a data frame. The router device checks whether the ZBLD source is listed in the neighbor table of the router device ("ZBLD € NT?"). If so, the device determines the relationship state ("ZBLD = child?"), And if it is a child, the router device sends a MAC ACK frame to the ZBLD ("MAC ACK").

If the ZBLD device is not listed in the neighbor table, the router device adds it with a state of "no relation". The router device then determines a performance indicator, eg, a link cost indicator for the wireless link from the child or the number of packets already received from this device (“PERF IND”). In addition, the link cost will be used as an example of a performance indicator. If the link cost indicator is better than a predetermined number, for example 3, the router device triggers a proxy resolution procedure after a random delay.

The proxy resolution procedure includes the following steps.

The first ZigBee router, which has a link cost for a ZBLD of less than 3 and receives a trigger for a proxy discovery procedure from the ZBLD, is itself addressed to all other routers in the network and is willing to become a new proxy for this particular ZBLD. Send a three-hop broadcast (ie, a broadcast range or survival time of two) indicating the intent of the "Proxy Resolution" message.

Upon receiving this message, the second router stores the proxy resolution message in memory, avoiding duplication, and broadcasting it again.

If the ZBLD originating the proxy search is not listed in the neighbor table of the second router, then no action is taken: however, if the ZBLD is listed, the second router is based on the performance indicator for the ZBLD and resolves the proxy. Based on the message, a comparison is made to determine whether it should act as a router for ZBLD.

The selection between the first router and the second router to act as a router for ZBLD may be made according to different criteria. In an embodiment, the second router compares the originator address in the proxy resolution message, which is the address of the first router device, with its address. If its address is smaller and the cost link is appropriate according to the predetermined cost link indicator used in the method, the second router device will be a proxy. Accordingly, it triggers "proxy resolution" using its address as the originator.

If the address of the second router is lower, but the link cost is inadequate, the second router only re-broadcasts the proxy resolution message received from the first router.

Next, we discuss the implementation details in 802.15.4 / Zigbee.

The implementation of the trigger of the proxy search procedure as a "proxy search" command frame on the MAC layer ensures that the command is very short, thus avoiding higher layer overhead, or network and application layer overhead in 802.15.4 / ZigBee. This increases the chance that ZBLD can transmit it by using the limited energy that ZBLD is self-contained. The only data required for this command is the identifier of the ZBLD (already in the 802.15.4 MAC header) and therefore the "proxy search" frame may be without payload. In order to make the packet shorter, the destination address and destination network identifier (from 802.15.4 / Zigbee: PAN identifier, PANId) can be omitted and only the source address and source network identifier PANID can be transmitted, and Intra-PAN of frame control Bit will be set. Thus, the total length of the "search for proxy" command (incl. PHY layer overhead) will be 15B.

Since the broadcasted "proxy resolution" is only sent over two hops, it is much shorter than the ZigBee nwkBroadcastDeliveryTime of 10s (for ZigBee PRO) to be repeated discovery if necessary, and to clear the BTT within a reasonable time. It must be maintained within the BTT for an hour. The "Resolve Proxy" command may be located at or above the network layer, for example, a Zigbee network status command may be used with the new status code.

In another embodiment, the trigger for the proxy search procedure may be part of a data frame, for example one of the reserved sub-fields of the MAC or NWK frame control field. This has the advantage of increasing the chance of obtaining the original ZBLD control message.

Although other methods in the invention include features that choose between several potential routers, it may occur that the proxy resolution protocol allows two routers to take the role of proxy independently for a particular ZBLD. This situation can occur in networks with highly variable router densities, for example, as described in relation to FIG. In the figure, R1 only knows R5, but any other nodes R2 to R4; R5 can know R3, and R2-R4 can all know each other. Accordingly, R1, R3, and R5 execute the resolution protocol, R1 with the lowest address acts as a ZBLD proxy, and independently R2-R5 execute the proxy resolution protocol, determining R2 to be a proxy. Ranges of router devices are indicated by dashed circles in the figures.

The situation is that the parent address is not included so routers cannot deduce it from the packets of ZBLD, and the two proxy routers R1 and R2 are not within range of each other, for example with respect to conflicting ACK frames. Because it is unknown, it cannot be found by routers.

One possibility is for ZBLD to discover ACK collisions and to restart the "proxy search" procedure over more hops, ie with a longer survival time.

Another possibility is to include the originator's address in the "resolve proxy" command, and-in the proxy resolution process-any of the intermediate nodes (in the example above, R3-R5) other competing proxies that had the lowest address before. Information about the router with the lowest address is sent regardless of the number of hoses, for example by unicast or by increasing the hop count to the packet being broadcast again.

Another possibility is that all routers in the vicinity of the ZBLD use the ZBLD's identifier as the group identifier, with all routers in the ZBLD's radio range being members of the group, which are initiated by any proxy discovery message and neighbor routers sent by the ZBLD. Any proxy resolution message can be addressed at this group address and thus have a good chance of reaching all router neighbors.

Optionally, the “proxy search” frame may have a two byte payload, containing an identifier of a group controlled by this ZBLD. This information, along with the information of a particular router that is a member of this particular group, must be carried in a "proxy resolution" frame exchanged by the routers. The resolution protocol could then be modified as follows:

Member routers use shorter random delays;

They stop the intended "proxy resolution" transmission only when they receive the same packet from another member router.

The new proxy is the member router with the lowest address.

As an alternative to all ZBLD neighbor routers buffering data frames during proxy timeout, only routers that are also neighbors of the ZBLD's proxy may do so, for example, by eavesdropping MAC ACKs sent by the proxy. . During the proxy timeout, they will monitor the MAC ACK to be sent, and if nothing comes, one of them will be handed over, ie retransmit the data packet and determine only among the routers previously listening to it, the "proxy resolution procedure" To start.

The word "a" or "an" before the element in the present specification and claims does not exclude the presence of a plurality of such elements. In addition, the word "comprising" does not exclude the presence of elements or steps other than those listed.

Reference signs in parentheses in the claims are for the purpose of understanding and not limitation.

Upon reading this, other modifications will become apparent to those skilled in the art. Such modifications may involve other features that are already known in the radio control networks technology and may be used instead of or in addition to the features already described herein.

Claims (15)

A method for wirelessly communicating in a network comprising a resource constrained end device, and a first router device, comprising:
The end device sending a trigger for a proxy discovery procedure;
The first router device receiving the trigger for a proxy discovery procedure;
Determining whether the first router meets conditions for operating as a router for the end device, and
If the conditions are met, the first router designating itself as a proxy router for the end device to relay communication between the end device and the rest of the network. . The method of claim 1,
The trigger for the proxy discovery procedure considers the identification of the end device, and the determining step includes:
Determining whether the first router device is linked to the end device based on the identification element,
Determining that the conditions are met if the end device is linked, and
If the end device is not linked, checking whether the first router device can link itself to the end device. The method according to claim 1 or 2,
Determining a performance indicator of the link between the end device and the first router device,
Comparing this performance indicator to a predetermined criterion, and
Determining that the first router device can be a proxy router for the end device if the performance indicator satisfies the predetermined criterion. The method according to any one of claims 1 to 3,
And the performance indicator is a link cost indicator. The method according to any one of claims 1 to 4,
And the performance indicator is the fact that the router application is controlled by the end device. The method of claim 1,
Sending the proxy resolution message by the first router device. The method according to claim 6,
And the proxy resolution message is sent between the end device and the first router device after a delay determined based on a performance indicator of the link. The method according to any one of claims 1 to 7,
The network further includes a second router device within a transmission range of the first router device, the method comprising:
The second router device receiving the proxy discovery trigger and / or the proxy resolution message from the first router device, and
A proxy router for the end device, wherein the second router device is based on the proxy resolution message and based on the end device identification and the performance indicator of the links between the end device and the first and second router devices. Determining whether to act as a wireless communication device. The method according to any one of claims 1 to 8,
The determination by the second router device is:
Determining whether the second router is linked to the end device,
The second router determining the performance indicator for the end device,
The second router comparing its address with the address of the first router device, and
If the address of the second router is lower than the address of the first router device, sending a proxy resolution message by the second router. The method according to any one of claims 1 to 9,
The network further comprises a third router device that is outside the transmission range of the first router device, the method comprising:
The third router device receiving the proxy search command frame,
Both the first and third routers meet the conditions for operating as a router of the end device,
The third router device designating itself as a router for the end device,
Both the first router device and the third router device send acknowledgment messages to the end device, and
The end device detecting a conflict between the acknowledgment messages and retransmitting a proxy resolution command frame. The method according to any one of claims 1 to 10,
Wherein a group identifier is used for communication of a proxy resolution command frame between the routers within a wireless range of a predetermined end-device. A method for communicating in a network comprising a resource constrained end device, and a first router device:
The end device sending a data frame to be delivered by a router device to a destination device,
The terminal device waiting for receipt of an acknowledgment message for a predetermined time, and
If no acknowledgment has been received, the terminal device executing the method according to claim 1. For the end device:
Wireless transmission means for transmitting data and triggering a proxy search procedure;
Wireless transmission means for receiving at least acknowledgment messages;
Means for tracking the acknowledgments and determining the proxy search procedure triggering; And
An end device comprising limited energy resources. For router devices:
Wireless receiving means for receiving data frames and command frames from other devices in a wireless network,
Wireless transmission means for transmitting acknowledgment messages and resolution messages,
Means for transmitting end device messages,
Comparison means for comparing the address of the router device with other addresses, and
Memory means for storing a neighbor table, the table comprising a list of end devices and a state of a relationship between the router device and each end device. 15. A radio control network comprising at least one device constrained with resources according to claim 13 and a router device according to claim 14.

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